NASA’s New Horizons probe is visiting Pluto — and just sent back its first color photos

No spacecraft has ever visited Pluto. That’s going to change on July 14, when NASA’s New Horizons probe will fly within 6,200 miles of the dwarf planet after a nine-year journey.

“This is pure exploration,” Alan Stern, the mission’s principal investigator, said during a Tuesday press conference in which the probe’s first color photos of Pluto and its moon Charon were released. “We’re going to turn points of light into a planet and a system of moons before your eyes.”

Next month, as New Horizons nears Pluto, it will start taking the most detailed photos we’ve ever seen of it. The craft will begin sending back atmospheric data on Pluto in May, and data on the dwarf planet’s surface composition in June. “By the time we get there in July, we will have returned over a thousand images to the ground,” Stern told me in a recent interview.

This is a big deal. Even though Pluto seems very familiar to us, we know far less about it than about any of the planets in our solar system. Two of its moons, Kerberos and Styx, have actually been discovered in the time since New Horizons left Earth in 2006.

In the 1960s and ‘70s, the Mariner missions showed us Mars, Venus, and Mercury, and in the 1970s and ‘80s the Pioneer and Voyager missions showed us Jupiter, Saturn, Neptune, and Uranus. In much the same way, this summer, New Horizons will give us a close-up view of Pluto for the first time.

New Horizons was launched in January 2006, and has now traveled about 2.9 billion miles from Earth, powered by an engine that harvests power from radioactively decaying plutonium pellets. In total, the mission will end up costing an estimated $700 million.

When the craft was launched, Pluto hadn’t yet officially been demoted from planet to dwarf planet, and the mission was initially billed as a visit to the solar system’s only unexplored planet. (In fact, Alan Stern has argued that Pluto should still be considered one.)

On the way there, in September 2006, the probe flew by Jupiter, taking photos of the planet (including the first close-ups of the Little Red Spot) and its moons, and using Jupiter’s gravity to slingshot out toward Pluto.

Since then, the probe has spent most of its time in hibernation mode, so as to conserve energy and extend the life of its hardware.

But starting in January, New Horizons began using several different instruments — including a few cameras — to gather data on Pluto. Because of the vast distance between it and Earth, that data will take about 4.5 hours to arrive, and it actually won’t be possible to send data at times, based on the probe’s orientation.

One of the most exciting things to come out of the mission will be the photos New Horizons takes of Pluto. Right now, the best images we have (taken by the Hubble Space Telescope) only show the dwarf planet as a blurry blob:

Next month, New Horizons will start taking sharper ones. As Emily Lakdawalla of the Planetary Society puts it, every photo the probe takes will be the best photo ever taken of Pluto. They may show polar ice caps, mountains, and perhaps even volcanic activity.

New Horizons will also take images of Pluto and its moons using visible infrared and ultraviolet wavelengths of light (which will tell scientists more about their composition), as well as stereoscopic cameras that will produce 3D topographic maps of Pluto’s surface.

Other instruments will detect particles escaping from the dwarf planet’s nitrogen-based atmosphere, while a radio antenna will send signals through it. By analyzing these signals after they pass through the atmosphere and reach radio dishes on Earth, we’ll get a better idea of the specific gases present in the atmosphere. Because the craft will collect so much data — and because it takes so long to send it back — it will actually continue transmitting it until 2016.

All this will be enormously valuable to scientists because we currently know so little about Pluto — and because it could help us better understand the formation of Earth and the rest of the solar system. “Pluto seems to be at the intersection of many important scientific questions about the accretion of planets and the loss of atmospheres, like the Earth experienced early in its history,” Stern told me. “We know that the Earth went through the stage of growth that Pluto stopped at. This will help us connect the dots.”

New Horizons will also collect lots of data on Charon and Pluto’s other moons. Data collected by New Horizons over the past year show that Pluto and Charon actually orbit each other — so much so that some scientists now consider it a binary system. Charon appears to have a much different composition than Pluto, and it’s hypothesized that it may have formed as part of a massive collision, just like the one that likely created Earth’s moon.

Assuming the craft is still operational after its Pluto flyby, scientists hope to use it to study more distant objects in the Kuiper belt — a region that contains more than 100,000 rocky objects, including Pluto. Stern and other scientists are currently deciding between two potential target objects, both about 30 miles wide. If all goes to plan, they’ll choose one next year, and New Horizons will arrive there in early 2019.